Marucci714

Hello fellow thirdgeners,

You guys have been a huge help in my previous cries for help and i've run into another situation hoping you guys will have some professional insight. First, i have an 86 Camaro, Vin H, carbureted, T-5 tranny & 305 swapped to 350. Goodwrench 350 290hp/350tq, yea i know nothing special buts its better than the beat up old 305 and was in the budget.

I forget the few gentlemen who helped me get my carb adjusted to run right as in setting the mixture screws for the MCS to 50% duty cycle or 30° dwell angle which i did with the vacuum ports plugged and hoses back on one at a time to ensure no changes due to a vacuum leak. The TPS is set at .40. The computer and distributor are talking and everything is running pretty good now. Except, my engine i guess i would say sputters or chugs in 4th and 5th gear. 1st 2nd and 3rd pull hard and drive as you would expect them to. Once I shift to 4th i can tell the engine feels like it falls behind the carb and has to "catch up", and no i'm not shifting too early. It drives and picks up speed slowly "sputtering" with no power, again, only in 4th and 5th gear. I'm guessing this isn't a secondary issue cuz it happens at all throttle positions(again in 4th and 5th gear only), in which the primaries do all of the work unless at WOT. Do you guys think i need to re-jet my primaries to make it a richer mixture? My feeling is i'm not getting sufficient fuel to the amount of air flowing through, but im a rook so i could use some help. I haven't gotten into the carb yet, so i don't know what mm my jets are just yet. Just wanted to get some opinions on what you think is going on? Maybe i do need richer jets since i moved from a 305 to a 350?

Also, just a side note, I have 1 code that constantly comes on and off. Map sensor. When i'm parked or idling or come to a stop the CEL is off, once i hit the throttle and the car starts to move, the CEL comes back on and its the Map sensor, on and off, on and off, on and off over and over again. I think the Map sensor affects the fuel trim, could this also be a factor? I replaced the connector as the other was pretty beat up, which didn't change anything, still comes on and off, just haven't replaced the sensor yet.

I would appreciate any knowledge you guys can drop on me, if you need anymore info i would be happy to provide that for you as well

Marucci714

Sorry to bump this thread but i could use some tech help..

*Edit - TPS is at .48 not .40

Im now thinking this ins't a carb or jetting issue. My feeling is that it may be timing related, but i'm pretty sure my timing is spot on as i've checked it multiple times. And IF it is my timing wouldn't my car run terrible at idle and 1st 2nd and 3rd gear as well?

I've been researching until my eyes bleed and brain hurts, and what i've come across is that the Knock sensor is relevant to engine size which i knew and I did put a knock sensor in for a 350 when i did the engine swap. But what i didn't do was replace the Electronic Spark Control Module and i see that this part could as well be relative to engine size? Is this correct?

Since the '86 Camaros and especially the carb'ed models did not come with 5.7L option, can i use one from say an '87 TPI model and would this have any effect in the way my car runs? Could it get rid of this sputter in 4th and 5th gear? Like i mentioned, car drives fantastic in 1st 2nd and 3rd gear...just not in 4th or 5th.. i'd like to drive my Iroc further than just around the neighborhood testing all the time, kind of pointless to take it anywhere else than that since i would eventually have to get into 4th and 5th gear at some point.

sofakingdom

iTrader: (1)

"Checking" the "timing" is WORTHLESS on a modified engine, other than adjusting it to where the engine runs the best.

In other words, try advancing and see what happens; if that makes it worse, try retarding it. If I were the betting kind though, I'd bet you won't fix the problem you ACTUALLY have by dinking with that, even though you can probably make it run about a hundred times better. Since your carb ECM is basically untuneable, the only handle you have on ignition timing, is twiddling it; which while you'll NEVER get it "the best it can possibly be" that way, at least you can find where it produces the best results for THE ENGINE YOU HAVE NOW, which is CERTAIN to be different from your original engine's "spec". (for that matter, the original engine would have run AHELLUVALOT better with the same treatment applied to it, since the "spec" isn't set up for the engine to run "the best", but rather, for lowest emissions and such as that)

What's ACTUALLY going on, sounds like fuel delivery. What that means is, as the car is sitting idling, the fuel system can flow enough fuel to keep the carb full; then as you take off and go through the first coupla gears the fuel system can't keep up, and the bowl drains down as you drive; then at some point the fuel level goes SO low that the engine can no longer pull fuel from the carb and it begins stumbling and stuttering. Sounds like that happens right about the top of 3rd gear in your case.

Replace the fuel filter.

Knock sensor and ESC won't cause your problem, much as "timing" can't and won't. Not saying "they're right", "they're the same", "the ones you have will work fine", or anything of the kind; just, they CANNOT cause the specific problem you are trying to fix. They are a detour AWAY FROM the true problem at hand. Focus on things that CAN cause a car to act like it's running out of fuel, which would of course be, the fuel system. Return to them later perhaps after you get the fuel system to keep the carb full at all times.

Marucci714

Thank you for your reply Sofa. I hear what you are saying regarding timing, my engine seems happiest at about 10°BTDC and that is where its at now. Like you said, i messed with timing a lot this weekend to no avail.

I understand what you are saying about not running at its peak performance with stock specs. I was using those stock specs as a base to work from, that other guys on here helped me get to with dwell angle and TPS and such so i as well used the "stock" timing as a base setting, which i thought should AT LEAST be enough for the car to run right, but just isn't the case as you stated.

My first assumption, even in my other posts where i got slammed by some guys, was a fuel delivery problem. i was told it was not a fuel problem, but a timing problem, and now i circled the wagon back round to the fuel system. BTW i just checked the fuel filter, it looked brand new still, and i replaced it anyways this weekend.

So you are saying that my float in my carb could not be set properly? or my fuel pump isn't pumping ENOUGH fuel? or my main jets need to go up in size, or something along that line?

I've got a new E4ME Quadrajet coming that is being dyno tuned. I figured having 2 can't hurt, i want to open the one i have now up and learn to rebuild it cuz its actually quite daunting to me thinking about rebuilding it myself. The place i originally got my carb from(the one im having problems with), i probably shouldn't have gotten from them in the first place...

sofakingdom

iTrader: (1)

You have a fuel delivery problem, one way or another, in some manner way shape or form.

If the car has EVER sat around non-running for more than a year or so at one time, then the fuel system is probably all plugged up with the usual crusties and tar and other crap that gasoline turns into over time. (it being intended to be used more or less immediately, and therefore not designed to sit around and remain stable) Not sure how you can look at a fuel filter of the type that's in a Q-Jet and tell very much about it; personally, if I went to the trouble of taking the line off to "look at" it, I'd FOR DAMN SURE put a new one in NO MATTER WHAT, as cheeeeeeeeeeeeeep as they are. But... the problem could also be this http://www.rockauto.com/catalog/more...nid=499&jpid=9 which is in the tank, or the tubing in the tank that it hooks to, in which case you'd need to just rod it out with a coat hanger and rifle brushes and such. Could even be the fuel pump but not likely, as fuel pumps usually fail some other way (like leaking gas into the oil). Any way you slice it though, it's most likely that the carb fuel bowl is running out of fuel after a period of high demand.

You can verify that FOR SURE by simply driving the car in some manner guaranteed to produce the symptom (like, up your favorite looooooooooooooooonnnnnnnnnnnnnngggggggg uphill expressway ramp) and as soon as the car really gets going good on the malfunction, take it out of gear and turn the engine Off (NOT all the way to "take the key out"!!!!!), pull off to the side of the road, and pop the air horn off the carb, and see how much fuel is in there. Remember, CUT IT OFF CLEAN AND COAST. Under NO circumstances let the engine idle, or let the engine brake the car, as that will allow the fuel system to refill the carb and thus hide what you're looking for; which is, to be able to peer into the fuel bowl AT THE EXACT INSTANT that the car is screwing up.

It's not the float. It's not the jets. It's fuel delivery.

Marucci714

Thanks Sofa, i hear what you are saying. The carb/motor were new, definitely hasn't sat around for very long if at all but a week or two without running. And yes, I DID replace the fuel filter when i checked the old one, I mean they are like 2 bucks, why not like you said.

And yea, the fuel pump is new as well, just a stock one from Autozone. i can't seem to find a better one anyways with the 'return nozzle' for the fuel return line. If you have any suggestions there i'm open ears. All the fuel pumps have an inlet from the tank and outlet to the carb, but not a third for the return. I don't think i need another one, but I have been searching around.

Understood on the diagnosing, didn't even know that there was a strainer like that in the tank or lines, i'll have to take a look at that. In any case, i have another Quadrajet on the way, as i doubt i'll be pulling over on the side of the freeway to take the Airhorn off the carb lol that takes some time unscrewing everything and pushing the roll pin for the fuel rod and the linkage for the primary and yea you know what it takes to do that im sure i don't have to tell you, let alone putting it back together hahahaha... Pretty sketchy, but i CLEARLY see what you are saying and how to do it.. I'll find somewhere to get it done.

Sofa - thanks again for your help sir, I genuinely appreciate you taking the time to help me.

sofakingdom

iTrader: (1)

I don't mean necessarily how much YOU let it sit around; if, let's say, 3 owners and 15 yrs ago, it sat around for 2 yrs, ...

The stock fuel pump is good for at least 400 HP so as far as that goes, you shouldn't have any trouble. Lots of people hallucinate that they need some other one, but it doesn't do them any good; only makes their car faster to the extent that it provides weight reduction, centered on the driver's wallet. Although, when I've operated them at that level, I've always found it helps to have one of these http://www.summitracing.com/parts/mor-65750/overview/ or equivalent. Keeping in mind, that when the cam PUSHES on the rod, the pump DRAWS IN (sucks) fuel from the tank; then, when the cam eccentric continues to rotate, the SPRING in the pump has to both PRESSURIZE the fuel and RETURN the rod back up into the block, meaning, that HEAVY AZZ stock push rod, limits high RPM fuel delivery SEVERELY. Not that that's your problem (yet), just a hint of things to come as you work through all the shortcomings of a "stock" car, which contains ALOT of things that are entirely good enough as-is for ALOT more power than "stock", yet all sorts of little gotchas are lurking in the shadows that you wouldn't suspect until you THIMK about it a bit after you run into the head-scratchers.

It's really not that tough to do the test I described... you don't have to take the carb completely apart, just, far enough to look in there with a NON-SPARKING kind of light. In/near OC, when I used to live out that way (N SD county) it was never too tough to come up with those long uphill kinda things where there was room to pull over and investigate.

Marucci714

Sorry you were talking fuel system and I'm thinking carburetor... I've been working too much lately... yes I'm sure the car sat for a while. PO was driving it when I bought it, but he got it from someone else. But I know all those headaches and gotchas you are talking about all too well unfortunately.. PO cut wires, removed emissions, modified original carb.. i put the emissions back in, figured out all the cut and/or missing wires, vacuum lines etc etc etc.. hoping to be finished with that stage after I figure out this fuel problem and map sensor circuit issue.

I don't see any reason not to put that fuel pump rod in for 25 bucks. I'd like to add on to the engine once everything gets finalized and the basics are done anyhow.

Speaking of the map sensor code, could that be playing a role in my fuel delivery issue? Code 32 map sensor circuit, CEL turns on as soon as the car gets going and turns off as soon as I stop. Everytime, never fails. And I'm not straying away from the fuel system as you mentioned, I will be pulling the tank down and replacing the filter and hoses and might as well blow the lines out.

sofakingdom

iTrader: (1)

MAP sensor thing is more likely the vac line disconnected. Wouldn't be related to the fuel system's ability to deliver enough fuel flow to keep the carb full.